The enzymes in liver and kidney which catalyze formation of sulfate esters of conjugated and unconjugated bile acids will be purified and catalytic activity will be characterized by standard kinetic techniques. Control of bile acid sulfation will be investigated by exploring the mechanism whereby estrogenic hormones and cholestasis affect the specific activity of bile acid sulfotransferase(s). The role of intracellular bile acid binding proteins in control of sulfation will be studied in vivo and in vitro.